Dewaxing of hydrocarbon oils



,Oct. 19, 1948. s, w, FERRls 2,451,545

DEWAXING OF HYDROCARBON OILS Filed Dec. 23, 1944 2 Sheets-Sheet l H Invenior t Seymour W .irerrif Oct. 19, 19478. ERRls 2,451,545

DEWAXING HYDROCARBON OILS Filed Dec. 25, 1944 2 Sheets-Sheet 2 H Ifivenior tiesi Seymour W fi'q-rr'is Q By AQey Patented Oct. 19, 1948 DEWAXING OF HYDROCARBON OILS Y Seymour W. Ferris, Mount Holly, N. J., assignor to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania Application December 23, 1944, Serial No. 569,603

2 Claims.

The present invention relates to the separation of oil-wax mixtures into solid and liquid components, and relates more particularly to the separation of wax from hydrocarbon oil-wax mixtures by means of a solvent or solvent mixture and a cerophile, i. e., an agent capable of preferentially wetting the wax.

In accordance with the present invention, I provide a process for separating solid wax from liquid hydrocarbon oil by transferring the solid wax from the oil into a liquid cerophile, thus forming a suspension of the solid wax in the cerophile, such transfer being effected in the presence of a solvent having a high solvent power for oil and a low solvent power for the cerophile and for the wax at the dewaxing temperature. 7

I have found that when an oil containing wax is diluted with a solvent having a high solvent power for oil and a low solvent power for wax, and the resulting mixture is commingled with a relatively immiscible cerophile at a temperature such that the wax is solidified, said cerophile being liquid at such temperature and having a preferential wetting power for the wax, the solid wax passes from the solvent-diluted oil into the cerophile substantially completely and forms a suspension therein which may be separated with the cerophile from the diluted oil, for example, by decantation or other means. The process of the present invention therefore involves the separation of two liquid phases, one of which contains the solid wax, which operation is far simpler and less expensive than the separation of solid wax from a liquid phase by filtration as in the commonly used acetone-benzol or propane dewaxing process.

Herein and in the appended claims, the term solvent is to be understood to comprehend a liquid which has a high solvent power for oil and a low solvent power for wax at the dewaxing temperature and which is capable of retaining in solution at such temperature the constituents of the oil-wax mixture other than wax, be they liquid parafiinic or naphthenic constituents, or asphaltic material. Such solvent is further characterized-in general, in having a higher specific gravity than the cerophile and in having a lowsolvent power for the cerophile and the solid wax at the dewaxing temperature. In, other words, the solvent must preferentiallydissolve the oil but not the wax at the dewaxing temperature,

and the resulting oil-solvent solution must be relatively immiscible with the cerophile and the wax, and therefore separable therefrom by decantation or other means.

Likewise, herein and in the appended claims, the term cerophile is to be understood to comprehend a liquid which preferentially wets the solid wax and permits it to pass from the oilsolvent phase into said liquid to form a suspension of solid particles therein. Such cerophile is further characterized, in general, in having a specific gravity lower than that of the solvent, and in having a low solvent power for both wax and oil in the presence of said solvent, and in being relatively immiscible with the oil-solvent solution at the dewaxing temperature, and therefore separable therefrom by decantation or other means.

In accordance with the present invention, an oil-waxmixture is commingled with a solvent and a cerophile, the temperature of the mixture is adjusted to cause crystallization or solidification of the wax if the wax is not already solidified, and the mixture is permitted to settle and stratify whereby two liquid phases or layers are formed, the lighter phase comprising the cerophile and solidified wax suspended therein, and the heavier phase comprising the solvent and oil substantially free of solidified wax. The phases are separated from one another by decantation or other means, and the solvent and cerophile are recovered from the respective phases by vaporization or fractional distillation. In many cases the solidified wax in the lighter phase will be found to have settled within the phase, in which case it is preferable to further decant the cerophile from the concentrated wax slurry prior to distillation of the slurry for the removal of the cerophile therefrom. The final products produced by this process are oil substantially free of solid wax, and wax substantially free of oil or containing a controlled amount of oil. Depending upon the choice of solvents and cerophiles, operating temperatures, and mode of operation, there may be produced oils of desired pour point varying, for example, from F. to +50 F., and waxes which may be substantially free of oil or containing oil in desired amounts, for example, of from 1% to 10% or more. In the preferred method of operation, I employ a multistage batch countercurrent system, or alternatively, a single stage continuous countercurrent system, as will be described in detail hereinafter.

In carrying out my pr0cess,'I may employ various'ratios of solvent to oil-wax mixture within the range of 0.5:1 to 4:1, depending upon the nature of the oil-wax stock, the nature of the cerophile, and the operating temperature. The solvent may comprise a single compound or a butene-l,

mixture of two or more compounds, and usually consists of a mixture of a polar compound and a non-polar compound in such a ratio that the resulting solvent will have a relatively high specific gravity, a relatively low freezing point, a high solvent power for oil and a low solvent power for wax at the dewaxing temperature, and will be relatively immiscible with the cerophile. The polar compounds, i. e., those having a dipole moment greater than 1 10 e. s. u., may be exemplified by nitrobenzene, o-nitrotoluene, nitrocumene, quinoline, o-chloraniline, ,8,B'dichlordiethyl ether (Chlorex) ethylene dichloride, furfural, methyl aniline, toluidine, Xylidine,

o-chlorphenol, benzonitrile, benzaldehyde, nicotine, and pyridine. The non-polar compounds may be represented by benzene, toluene, xylene, carbon tetrachloride, methyl chloride, chloroform, diethyl ether, and carbon disulfide. The

ratioof non-polar compound to polar compound m-ayvary fromv to 1.5 1, no non-polar compound beingutilized if the polar'compound per'se, fulfills the requirements withrespect to gravity, solvent power, freezing point, etc., as described abovewith respect to the solvent.

In conjunction with the solvent or solvents mentioned above, a cerophile is employed, the ratio of -,cerophile-to oil-wax mixture being within therange of 0.5:1 to- :1. The cerophiles, which are.substantiallynon-polar may be exempli ied by: liquefied ethane, ethylene, propane, propylene, n-butane, isobutane, 'isobutylene, butene-Z, the pentanes including neopentane, th e hexanes including neohexape, and the higher homologues of the parafiin andvg lefin series which are liquid at dewaxing temperatures. All of these-cerophiles have boilin pointsbelow that of the wax, and may be recovered, by distillation from the wax. On the othenhancl, it isalso possible to employ relatively parafilnic oilshaving a boiling point. above that of the wax, in.- which case the wax is recovered by distillin it from. the high boiling ceropl liler Such. high boiling parafiinic oils include theseleetive solvent rafiinatesidewaxed) from lubricating oil stocks, lubricating distillates or residuum from parafiinabase crude oils such as from -,l?ennsylvania, hydrocarbon polymers, and the like. In the dewaxing of heavy oil stocks, such, as .,waxy; residuums,.it is preferable to employlaqirelatively light cerophile suoh as liquefied ethane, propane orpropylene, or nixtures of two or more, thereof. With intermediate waxy stQcks, the butanes, pentanes ,;or hexanes are pre-- fe'rred, Andcwith very-light waxy stocks, the heavier orliigh boiling cerophiles are most satisiactory, particularly a dewaxed selective solvent raffinateof relatively'high. parafiinicity derived from a lubricating oil stock;

In dewaxing hydrocarbon oils to obtain 0 F. pour point oils, using the techniqueof the present,-.inven-tion-, a dewaxing temperature of 0 F. to. -10 F. is satisfactory. In the event that oils of higher or. lower pour pointare to be made, the dewaxing,temperatures may be increased or deereased; correspondingly. For the production of :low ;melting point. waXes,-,temperatures considerably below 0 F; may be employed, whereas fortheproduction of high melting point waxes, for example, thoseof 140 F. to 175 F. melting point, temperatures approaching ordinary room temperature: may; bev utilized.

My inyentionmay be further understood with reference; to the accompanying'drawing, in. which Figure 1 illustrates a 2-stage batch countercurrent system and Figure as single stage continuous countercurrent system suitable for carrying out my process.

Referring to Figure 1, oil to be dewaxed is supplied from tank I and cerophile is supplied from tank 2 by means of proportioning pumps 3 and .4, respectively, and the mixture is passed through pipes 5v and B to circulating pump 7. Simultaneously, the solvent containin oil dissolved therein is delivered through pipe 36 and pipe 6 to pump 1. The mixture of waxy oil, solvent, and cerophile is forced by pump 1 through the. cooler 8 whereinthe mixture is brought to the dewaxing temperature, for example, 0 F. and the wax is caused to solidify as fine crystals. The cooled mixture is then delivered by pipe 9 to mixer It provided with stirring means I l, and the components of the mixture are vigorously agitated to insure thorough contacting thereof. The mixture is then passed by means of pipe 12 into settlin vessel !3 provided. in its upper section with stirring means M. Settling and stratification of the mixture results in the formation of two immiscible phases or layers, the upper and lighter phase comprising the cerophile with substantially all of the finely divided solidified wax suspended therein, and the lower andheavierphase comprising the. solvent and oilsubstantially freeof solidified wax. It will be understood, of course,- that while the phases are substantiallyimmiscible, a small amount of solvent and oil will be dissolved or entrained in the lighter phase, and asmall amount of cerophile from the lighter phase will be dissolved or entrained in the heavier phase. The heavier phase comprising essentially solvent and. oilis withdrawn from. the bottom of settling vessel l3.,and passed through pipe l5 into fractionating. tower It? provided with heating means. such, as steam coill'l'. In tower I6 the solvent is. vaporized and stripped from the oil, and thedewaxed oil substantially free of solvent is withdrawn from the bottom of the tower through. pipe l8 and passed to storage not shown, The solventwhich has been vaporized from the oil is removed: from .th'etop ofthe tower, condensed. by condenser 19 and. collected in receiver 28, from whence itisdelivered by pump 2| and pipe-22 into. pipe 23 ,for further use, as Will be described in detail. hereinafter.

Referringragain tosettling vessel E3, the lighter phase. comprising the cerophile and solid wax dispersed, therein iswithdrawn through pipe and delivered bypipe 23 tucirculating pump 25 together with recovered solvent. from pipe 22, fresh solvent being supplied from tank 26' by proportioning. pump]? and pipe 28 as needed. Since there is a tendency for the solidified wax particles to settle inthe cerophile it maybe neces-. sary to apply slowagitation. tothe lighter phase in settling vessel Itflb-y means of stirring means M, thus. providing. a, uniform dispersion of. wax

in the cerophi1e for withdrawalv through ipe 24;

Pumpififorces, themixture of solvent, cerophile andwax containing minor amounts of ,oil through cooler. 29 whereinthetemperature is again adjust-ed if,-necessary, .forexample, .to 0 F., and the cooledmixture ispassed through pipe 39 into mixing vessel 3 lprovided withstirn'ng means 32. Herein the mixture is thoroughlyagitated to effect intimate contact. betweenthe relatively im-. misciblesolvent, cerophile, and wax. The mixture is then delivered by pipe 33, to settling vessel etc-provided with, stirring, means. 35,, andis permitted to settle andstratify, wherebythere are formed two immiscible liquid phases or layers,

the upper and lighter phase comprising'the cerophile and solidified wax particles relatively-free of oil, and the lower and heavier phase comprising the solvent containing the residual oil but substantially no solid wax. The heavier phase is drawn from the bottom of vessel 34 and passed by means of pipe 36 into pipe for further use in the treatment of the original oil-wax mixture in mixer Ill and settler 13. To prevent settling of the wax particles in the cerophile, the upper phase or layer may be slowly agitated by the stirring means 35, and the cerophile and suspended wax is withdrawn from the vessel 34 by means of pipe 31 and delivered to an auxiliary settling vessel 38, in which the wax particles, by virtue of their higher specific gravity, settle through the cerophile and accumulate as a wax slurry in the lower section of the settler 38. From the upper section of this settler, cerophile substantially free of wax particles is withdrawn and passed by pump 39 and pipe 40 into pipe 6 for recycling to the initial oil-wax mixture to be treated in mixer ii! and settler Hi. The slurry comprising wax particles and cerophile is withdrawn from the bottom of settler 38 and passed by pipe 4| into the iractionating tower 42 provided with heating means such as steam coil 43. In this tower the cerophile is distilled or stripped from the wax, the wax being withdrawn from the tower by means of pipe 44 and passed to storage not shown. The vaporized cerophile is passed from the top of tower 42, condensed in condenser 45 and delivered from receiver 46 by pump 4'! through pipe 48 to pipe 6 for reuse in the treatment of additional quantities of the initial oilwax mixture. The auxiliary separator 38 affords a simplemeans for separating the bulk of the cerophile from the wax, and simultaneously reduces both the load upon the fractionating tower 42 and the content of oil which would normally appear in the wax had the entire stream from pipe 31 been charged directly to tow r 42. In the event that it is desired to fractionally distill the entire stream from pipe 3 proper ma-. nipulation of the valves in pipes 31, M, and 49 will permit the entire stream to enter the tower 42 via pipe 49.

While the above batch countercurrent operation has been described with reference to only two stages, it is obvious that the number .of

stages may be increased by inserting between the first and last stages, the desired number of additional coolers, mixers, and settlers to give a total of 3, 4, 5, or 6, or more stages. In any case, regardless of the number of stages, the operation is carried out in a continuous manner; employing the well-known countercurrent contacting principles.

packing, if desired. Such solvent is supplied from solvent tank 60 by means of proportioning pump Bl, cooled to the dewaxing temperature, for example, of -l0 F., in cooler 62, and passed by circulating pump 63 and pipe 64 into tower 59 at a point somewhat below the top of the tower. The finely divided mixture of wax, oil, and cerophile from the spray head 58, being of lower specific gravity than the solvent, rises through the solvent contained in the tower, and during the intimate countercurrent contact with the solvent, the oil is dissolved from the wax and the cerophile, with the result that there accumulates above the solvent phase in the tower, a second immiscible phase comprising cerophile containing a suspension of finely divided solid wax particles substantially free of oil, or containing a controlled amount of oil. This lighter phase containing the cerophile and solid wax with traces of dissolved or entrained oil is withdrawn from the top of tower 59 by means of pipe 65 and delivered to an auxiliary settling vessel 68, in which the wax articles, by virtue of their higher specific gravity, settle through the cerophile and accumulate as a wax slurry in the lower section of the settler. From the upper section of this settler, cerophile substantially free of solid wax particles is withdrawn and passedby pump 6! into pipe 54 for recycling tothe initial oil-wax mixture to be treated in contacting tower 59. The slurry comprising wax particles and cerophile is withdrawn from the bottom of settler 66 and passed by pipe 68 into the fractionating tower 69 provided with heating means such as steam coil ll]. In this tower the cerophile is distilled or stripped from the wax, the wax being withdrawn from the tower by means of pipe H and passed to storage not shown. The vaporized cerophile is passed from the top of tower 69, condensed in condenser 12 and delivered from receiver 13 by pump 14 to pipe 54 for reuse in the treatment of additional quantities of the initial oil-wax mixture. In the event that it is desired to fractionally distill the-entire light phase comprising cerophile and wax withdrawn from the top of contacting tower 59, proper manipulation of the valves in pipes 65, 68, and 15 will permit the entire stream to enter fractionating tower 69 via pipe 15.

Referring again to contacting tower 59, the heavier phase comprising solvent and oil substantially free of solid wax, is withdrawn from the bottom of such tower and introduced by pipe l6 into fractionating tower Tl provided with heating means such as steam coil 18. In this tower the solvent is fractionally distilled from the oil, the

The process of the present invention may also be carried out in a single stage continuous countercurrent system such as that illustrated in Figure 2 of the drawing.

Referring to Figure 2, oil to be dewaxed is supplied from tank 50 and cerophile is supplied from tank 5| by means of proportioning pumps 52 and 53, respectively, and the mixture is passed through pipe 54 to circulating pump 55, which forces it through cooler 56, wherein the mixture is brought to the dewaxing temperature, for example, -l0 F., and the wax is caused to solidify as fine crystals. The cooled mixture is then delivered by pipe 51 to the spray head 58 disposed in the lower section of contacting tower 59, and is thence sprayed into the body of cooled solvent contained 'in the tower. The tower may be provided with oil being withdrawn from the bottom of the tower through pipe 19 and passed to storage not shown. The vaporized solvent is passed from the top of the tower, condensed in condenser 80, and delivered from receiver 8| by pipe 82 to ump 6| for reuse in the treatment of additional quantities of the initial oil-wax mixture.

The dewaxing systems described with reference to Figures 1 and 2 are designed for operation with solvents and cerophiles, both of which have boiling points lower than those of the oil and wax. In the event that the solvent or the cerophile or both, are higher boiling than the oil and the wax, the fractionating equipment and recirculation system must be suitably modified to take overhead the wax and the oil, and to leave as distillation residues, the solvent and the cerophile. When the solvent is lower boiling and the cerophile is higher boiling than the oil and wax, the solvent is taken overhead, and the cerophile is taken as a residue. Such modifications are obi ls-515.5453

Z vi'ouslywithin the;v skill: oi: those, iamiliar with theart, and require no further elaboration.

The.- following examples. are. illustrative of: the results: which may be obtained in thepractice oi the. present invention, but: are: not to be con strued as. limiting. the scope thcreofi.

I. The hydrocarbon. oil'stoclssto= bei dewaxed wasv aidistillate from. a wax-bearing crude,. such distillatehaving thefollowing properties; and contain.- ing' approximately 10% of; crystallizable parafiin hydrocarbons- Pour point F; 30 S. U. vis., 100 F'. seconds 42 A. P; I; gravity degrees 3514 Boiling range (10' mm. pressure')- F- 138-448 The cerophileemployed. was. prepared from a dewaxed, solvent extracted vacuum still.- overhead from/a. crude residuum, such overhead fraction having the following properties:

Pour point F 5 S..U. vis., 100 F seconds 815 A, P. I. gravity degrees 2.7.9

This-overhead fraction was mixed with an equal volume of ethylene dichloride and the mixture 'Wascooled to +5 F.', at which temperature two liquid phases were formed andpermitted to stratify' into layers. The lower layer comprising a major portion of the ethylene dichloride and the more 'na-phthenic constituents of the oil dissolved therein was separated from the upper'la-yer comprising that portion of the oil insoluble in the ethylene dichloride and containing an equilibrium amount of ethylene dichloride dissolved therein. This upper layer constituted the cerophile.

In carrying out the present invention, 1-20 volumes of hydrocarbon oilstock first described was admixed with 1-20 volumes of the cerophile and 480 volumes ofsolvent consisting of ethylene dichloride, the temperature being about 75 F. This mixture was then cooled; with agitation, to F., during which step a portion of the crystallizable parafiinic constituents ofthe oil stock crystallized in the form of small, solid particles and two liquid phases formed. Agitation was stopped, and the'mixturewas permitted tosettle. 'I-wo immiscible layers were formed,- the upper layer comprising the cerophile containing a suspension of solid crystals, and the lower layer comprising the solvent, i. e.,- ethylene dichloride; containing the oil dissolved therein. Thelayers were separated from one another, and the ethylene dichloride was removed by vaporization. There was obtained from the lower layer 54% of the noncrystalli'zable constituents of the origin-alioi-l. stock, while the crystallizable constituents were concentrated in the remaining46%- of the oil" stock contained in the cerophile. By employing multistage-batch or continuous countercurrent operation, in lieu of the single stage batch separation above described, the quantity' of oilassociated with the crystalli-zableconstituents contained in the cerophile could be markedly-reduced,"and if desired, such crystal-lizabl'e constituents could: be obtained substantially oil-free.- The. crystallizable constituents may be separated from. the cerophile by distillation, preferably at reduced pressure.

2. In this example, the oil stock to bedewaxed comprised a. solvent extracted waxrbearing parafl'inic oil containing approximately 12% of wax, and having a pour point of +80?" a. Saybolt: Universal viscosity of: 44. seconds at 210 E" and.- .an A., 2;. I... gravity" of: 31.3.; lihe :oilz. solvent comprisedlamixtureof 4.7% by: volume; oi'o-nitro toluene, 38.5% by volume of nitrobenzene, and 14.5%. by volume. of toluene. The cerophile come prised commercial. liquid propane having the mole percent composition of 82.31% propane, 13.5%. propene, 3;2.% ethane. 0.6% .isobutane, and. 013% ne-butane.

1-82..volumes of the. oil stock, 636 volumes of the oil; solvent, and. 18 2'. volumes: of. the. cerophile were, thoroughly mixed.- at. 2.0 F. for 3ll.minutcs:,. under sufiicient. pressure to. maintain: the. mixture in the. liquid phase. At this. temperature the Wax crystallized in. the form of solid. particles; The agitation was then stopped, and they mixture wasv permitted to settle. and stratify into. two liquid layers. Theupper layer comprising the cerophile containing: a suspension of. crystallized wax; and a small. amount of. solvent and oil.- in solution, was separated from the lower layer comprising the oil: solvent containing the. major portion; of the. oil. in solution'and a minor amount of cerophile, but no. crystallized wax. The cerophile. layer then-thoroughly mixed with 550 volumes of fresh oil. solvent comprising;51% by-volume of; o-nitrotoluene, 41.6% ,by volume of nitrobenzene, and 7-.!% by volume of toluenethe temperature-being heldat 20 F; under pressuresufiicientto main= tain. the mixture in the liquid phase. The. mix.- ture was. permitted to settle. andastratify into. two liquid. layers, the upper layer comprising the cerophile andcrystallized wax, and the lower layer comprising the oil solvent containing. a small amount of dissolved oil but no solid wax, and the layers were separated. The lower layers from the two treatments. above described were combined and. subjected-to distillation at reduced pressure to remove the oil solvent and traces 'of cerophil'e. The distillation residue comprisinga d'ewaxed oil having a pour point of5-" a Saybolt Universal viscosity of 46 seconds at 210 F-., and an A. P..I. gravityof 281. The cerophile layer from the second treatment, after removal of the cerophilebyvaporization, comprised a hydrocarbon waxof lowoil content.

31 The oil stock to bedewaxed' was the same as that employed in Example 1-, the solvent was ethylene dichloride, and. the cerophil'ewas a dewaxed, solvent, extracted vacuum still overhead from a crude residuum, such. overheadhaving an A. P; I. gravity of 27.9 and a Saybold Universal viscosity of'8-15 seconds at 100 F.

Equal volumes of the oil stock and the comphile were mixed, and the mixture was treated with the solvent in a 3-stage batch countercurrent system similar to that illustrated' in Figure 1 of the drawing, the cerophile-oil stock mixture being charged at the rate of 1 volume to every 4 volumes of solvent used, the temperature'of'separation Of the crystallizable constituents, of. the oil stock being maintained at 0, F. After the system had reached equilibrium, the solvent phase was found to contain of the oil constituents of the stock, whereas the crystallizableconstituents. or waxf was concentrate ed in the remaining 5%. contained in the corephile. The wax. recovered from the cerophi-le by distillation. had a. melting point. of. 61F.

Other combinations of. solvents and cerophiles which may be suitably employed in accordance with this invention: are exemplified by the following, it being understood that; the ratio.- of the components. of the solvent, as :well asthe ratio of solvent to cerophile maybe varied considerably fromthe values given: below. The. parts of The process of the present invention is applicable not only to the separation of crystallizable hydrocarbons usually referred to as wax and having melting points above 110 F., but is likewise adapted for the separation of crystallizable hydrocarbons having melting points lower than those usually associated with wax. For example, in accordance with the present invention, it is possible to separate from hydrocarbon oils, crystalliza-ble hydrocarbons having melting points below 100 F., i. e., the so-called liquid waxes. Furthermore, by operating at very low temperatures, for example, 50 F. to l50 F. it is possible to separate from a dewaxed oil, certain fractions which at ordinary temperatures appear as viscous liquid hydrocarbons. The present invention is also adapted to the separation or purification of various materials other than hydrocarbon wax. For example, animal and vegetable fats and waxes may be refined by my process, as may be rosin, stearic acid, crystallizable coal tar derivatives such as naphthalene, anthracene, and carbazole, and many other substances comprising mixtures of crystallizable and non-crystallizable compounds.

Hydrocarbon oils which may be subjected to treatment in accordance with the present invention include parafilnic oils, paraflin distillate, intermediate distillate, residuums, oils from the destructive hydrogenation of carbonaceous materials, cracked tars, polymers, and the like. The wax-bearing oils which also contain asphaltic material may be subjected to a premilinary treatment for the removal of asphalt, for example, by

precipitation with liquefied normally gaseous hydrocarbons, or by treatment with chemical agents such as sulfuric acid, aluminum chloride, or other refining agents.

Furthermore, the waxy oils may be dewaxed by my method and the dewaxed oil then separated into liquid fractions respectively more paraflinic and more naphthenic than the original oil. This may be accomplished in a relatively simple manner by modifying the solvent power of the solvent in the oil-solvent phase resulting from my dewaxing operation. For example, a wax-bearing oil is dewaxed by treatment with a cerophile such as liquid propane and a solvent which has a high solvent power for oil but not for wax, e. g., a mixture of nitrobenzene, o-m'trotoluene, and toluene. The cerophile-Wax phase is separated from the oil-solvent phase, and the toluene is removed from the later phase by distillation. Upon removal of the toluene, the remainder of the solvent, i. e., nitrobenzene and o-nitrotoluene becomes selective as to the liquid constituents of the dewaxed oil, and as a result of this selectivity, a separation of the oil-solvent mixture into two immiscible liquid phases or layers is effected. One phase comprises the major portion of the more paraffinic oil constituents in which is dissolved a minor portion of the solvent, and the other phase comprises the major portion of the solvent in which is dissolved the more naphthenic oil constituents. Upon separation of the phases and removal of the solvent from each, there is obtained a liquid paraffinic oil fraction and a liquid naphthenic oil fraction.

It is, of course, possible to reverse the order of these operations, namely, to efiect the selective solvent separation of the oil into parafiinic and naphthenic oil fractions, and then dewax the paraffinic oil fraction by the method of the present invention. For example, the wax-bearing oil stock may be treated first with nitrobenzene or a mixture of nitrobenzene and o-nitrotoluene, or any other conventional selective solvent, whereby there is obtained a phase comprising wax, paraffinic oil constituents, and a. minor amount of solvent. and a second phase comprising the major portion of the solvent and the naphthenic oil constituents. After separation of the phases, the wax-containing phase is admixed with a cerophile such as liquid propane and the mixture is treated with an oil solvent such as a mixture of nitrobenzene, o-nitrotoluene, and toluene, whereby two immiscible liquid phases are formed, one comprising the cerophile and the wax, and the other comprising the solvent containing the dissolved paraflinic oil. The phases, after separation and removal of cerophile and solvent, yield wax and dewaxed paraffinic oil, respectively. If desired, the initial selective solvent extraction of the waxy oil stock may be carried out in the presence of ,liquid propane or other low boiling, relatively paraffinic hydrocarbons.

The oils or waxes separated in accordance with this invention may be subjected to subsequent refining operations, such as sulfuric acid treatment, aluminum chloride treatment, or treatment with adsorbents such as fullers earth, bauxite, or the like. In the dewaxing of crude residuums in accordance with the present invention, it has been found that any inorganic salts which may be present are removed together with the wax. It appears that the salt particles, particularly sodium chloride associated with crude residuums from certain sources, are coated or enveloped with a wax film, and that such salt particles, therefore, act as wax, and are incidentally removed during the dewaxing operation.

From the description of my process and the various modifications thereof given herein, it will be evident that the successful operation thereof depends upon the use of a polar oil solvent and a non-polar cerophile, the oil solvent being of such composition as to be relatively immiscible with the wax and the cerophile at the dewaxing temperature, and the cerophile being relatively immiscible with the solvent, the oil, and the wax at such temperature, the cerophile being further characterized in its ability to preferentially wet the wax in the presence of the oil and solvent and to transfer the wax from the oil and solvent, and thus make possible the separation of two immiscible liquid phases, one comprising the serophile and suspended solid wax, and the other comprising the solvent and the oil substantially free of solid wax. Thus the process of the present invention differs from the conventional solvent dewaxing processes in which the oil and solvent forms one liquid phase from which the solid wax is filtered, and likewise differs from the conventional selective solvent extraction processes-- in which the oil is separated intotwo liquid fractions, one being relatively more naphthenic and tl'ie-- other relatively more parafiinic than: theoriginal oil, any wax content of; the original oil being concentrated in the moreparaf= finic liquid oil fraction which must subsequently be deWaxed by the present process or by the cone ventional dewaxing methods known to the art;

Herein, the particular solvent or solvent combination has generally been referred to as being polar, i. e., having a dipole moment greater than 1 1-0 'e. s. u.', While the cerophile or cerophile combinations. have generally been referredto as being non-polani. e., having a dipole moment less than 1 1()- as u. It is to be understood, however, that such definition is arbitrary, and

thatthe oil solvents are relatively polar with respect to the cerophiles. For example, nitrobenzenehas a dipole moment of 3.9, o-nitrotoluene 3.7, furfural 3.57, pyridine 2.1, and ethylene dichloride 1.8, such compounds representing the oil solvents. or components of the oil solvents. Thecerophiles are generally less polar than the oil solvents, and compared with the oil solvents, have lower dipole moments, for example, the. liquefied normally gaseous hydrocarbons and the liquid paraflinic hydrocarbons have dipole moments of Iclaim:

1'. The method of dewaxing an oil-waxmixture which comprises commingling the oil wax' mixture with a solvent anda cerophile at a temperature at which the wax is solidified, said solvent comprising a mixture. of toluene, nitrobenzene, and o-m'trotoluene, and said cerophile comprising a liquid parafllnic hydrocarbonfiormingg in,-.and theheavier onecomprises thesolvent and oil substantiallyfree o-fsolidified wax; separatingthe lighter. phasenirom the heavier phase, and; removing the'waxfrom the lighter phase and the solvent from the heavier phase.

2. The method of, dewaxing an oil-wax mixture which comprises comminglingthe' oilewax:

mixture with a solvent and acerophile at a tern:

perature at which the wax is solidified, said sol vent comprising aumixture of toluene, nitrobenr zene, and o-nitrotoluene, and saidcerophile com-. prising a liquid parafiim'c hydrocarbon, forming two immiscible liquid phases of difi'erent specific gravities of'which' the lighter one comprises the cerophile and the'solidified'wax suspendeditherein, and the heavier one comprises the 'solvent'and' oil "substantially free of solidified wax, and separating-the lighter phase from the heavier-phase:

SEYMOUR, W: FERRIS.

REFERENCES CITED The following references are of file of this patent:

UNITED STATES; PATENTS:

record ,1 in the: 

